This project is comprised of methodologic research studies that explore exposure assessment methods to further understand and define relationships between nutrition and the development of cancer. In one study, participants consumed meat cooked at both high and low temperatures for one week each. Multiple types of biological samples were collected over this time period to investigate biomarkers of meat intake. Another biomarker based evaluation is the Observing Protein and Energy Nutrition (OPEN) study, which investigated the accuracy of alternative dietary assessment instruments. Two dietary data collection instruments, The NCI Diet History Questionnaire and the 24-hour dietary recall interview, were compared using two biomarkers: doubly labeled water and urinary nitrogen excretion. To estimate intake of heterocycic amines and benzopyerne in cooked red meat, meat samples were cooked to different degrees of doneness and then measured for heterocycic amines and benzopyrene. From this data, study collaborators then developed a food frequency questionnaire (FFQ) with a cooked meat module, along with databases to be used in conjunction with the FFQ. Two additional areas, processed meat and iron exposure in relation to cancer risk, are also being pursued. To investigate these hypotheses, the cooked meat module has been expanded to include detailed information on processed meats and fish. Two additional databases, one for total iron and heme iron in cooked meat and the other for nitrite, nitrate, and N-nitroso compounds in processed meats are under development as well. Additionally, a database to calculate glycemic index values has also been established and is used to determine glycemic index values in five types of food frequency questionnaires. The development of an internet-based physical activity assessment for application in AARP and other cohorts is also underway. The activities include literature review, questionnaire design, cognitive interview testing, development of a web-based system for questionnaire use, usability testing, and pilot studies. Several other methodologic studies designed to improve quality of dietary assessment methods and to further validate studies of food frequency questionnaires used in NEB studies have also begun.